The modern athletic shoe is a highly refined combination of many elements which have specific functions, all of which must work together for the support and protection of the foot during an athletic event. A shoe is divided into two general parts, an upper and a sole.
The upper is designed to snugly and comfortably enclose the foot. Typically, it will have several layers including a weather- and wear-resistant outer layer of leather or synthetic material such as nylon, and a soft, padded inner liner for foot comfort. Current uppers typically have an intermediate layer of a synthetic foam material. The three layers of the upper may be fastened together by stitching, gluing, or a combination of these. In areas of maximum wear or stress, reinforcements of leather and/or plastic are attached to the upper. Examples of such reinforcements are leather toe sections attached over synthetic inner layers of the toe area and heel counters made of an inner layer of plastic and an outer layer of leather. In competitive track events it is important to keep the weight of the upper as low as possible.
The other major portion of an athletic shoe is the sole. Designed to withstand many miles of running, it must have an extremely durable bottom surface to contact the ground. The ground contact surface of an athletic shoe includes traction elements or cleats to enhance the reaction between the foot and the ground. Enhanced traction is particularly important in competitive track events. Thus, track shoes frequently incorporate spikes in the forepart portion of the sole. The spikes are thin metal projections, which are typically removable from the sole. The forepart portion of the sole of a track shoe is typically made of a relatively hard material such as nylon in order to provide a sturdy base for a socket to hold the spikes, and is typically referred to as a spike plate. Prior art spike plates typically extended only under the forepart portion of the shoe, with the remainder of the sole being formed of a more resilient plastic or rubber material. In track shoes where additional shock absorbency is desired, a more resilient material is extended over the spike plate and the remaining length of the shoe, with appropriately located holes through which the spikes can extend, and a relatively thin shock absorbing midsole layer is added in the heel and arch area.